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JEE Main 2023 (29 Jan, Shift 2) · Polarisation

Polarisation question from JEE Main 2023 (29 Jan, Shift 2)

Q39JEE Main 2023 · 29 JAN · SHIFT 2Medium

Polarisation

Unpolarised light is incident on the boundary between two dielectric media, whose dielectric constants are 2.8 (medium −1-1) and 6.8 (medium −2-2), respectively. To satisfy the condition, so that the reflected and refracted rays are perpendicular to each other, the angle of incidence should be tan⁡−1(1+10θ)12\tan^{-1}\left(1 + \frac{10}{\theta}\right)^{\frac{1}{2}} the value of θ\theta is __________.

(Given for dielectric media, μr=1\mu_r = 1)

Numerical answer type. Work it out, then open the answer.

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Answer: 7

  1. With μr=1\mu_r = 1, refractive index n=Kn = \sqrt{K}, so tan⁡iB=n2n1=(6.82.8)1/2\tan i_B = \frac{n_2}{n_1} = \left(\frac{6.8}{2.8}\right)^{1/2}
  2. 6.82.8=1+42.8=1+107\frac{6.8}{2.8} = 1 + \frac{4}{2.8} = 1 + \frac{10}{7}
  3. Comparing with (1+10θ)1/2\left(1 + \frac{10}{\theta}\right)^{1/2} gives θ=7\theta = 7.
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